Electrical system enclosure with mounting brackets incorporating local inductances

Abstract

The invention relates to an electrical system (30) comprising: - a housing (31) having a supporting side panel (33.1) forming a heat sink (35) for the power transistors or behind which is a finned heat sink, - said supporting side panel (33.1) having mounting tabs (37), - the mounting tabs (37) projecting beyond a thickness of the supporting side panel (33.1), such that the supporting side panel (33.1) is positioned at a distance from the chassis, - each mounting tab (37) having a corresponding local inductance (40), such that a common-mode current from the power transistors and passing through the heat sink (35) can be channeled to the chassis via the local inductances (40) of the mounting tabs (37) forming a high-frequency impedance path between the heat sink (35) and the chassis. Figure for the abstract: Figure 2a

Description

Title of the invention: ELECTRICAL SYSTEM HOUSING WITH MOUNTING BRACKS INTEGRATING LOCAL INDUCTANCES

[0001] The present invention relates to an electrical system housing comprising mounting tabs incorporating local inductances. The invention finds a particularly advantageous, but not exclusive, application in the field of power electricity with electrical circuits associated with high-power rotating electrical machines equipping a vehicle, in particular an aircraft.

[0002] Figure 1 represents a conventional electrical architecture 10 comprising two static electrical converters, namely a rectifier 12 capable of transforming a polyphase alternating voltage into a direct voltage and an inverter 14 capable of transforming a direct voltage into a polyphase alternating voltage. The electrical architecture 10 comprises an alternating network 16 for supplying a load 18, such as, for example, a polyphase electric motor, through the rectifier 12, generating a direct voltage from the alternating voltage from the alternating network 16, and through the inverter 14 supplying a polyphase alternating voltage to the electrical load 18 from the direct voltage.

[0003] The inverter 14 is mounted on a heat sink for cooling. The inverter 14 has three bridge arms 14u, 14v, and 14w (one per phase), each having two transistors, for example MOSFET or IGBT (Insulated Gate Bipolar Transistor) type, controlled in on / off mode. Each transistor can be associated with a diode. In the example shown, the three-phase electrical load 18 has three phases, each connected to a corresponding bridge arm 14u, 14v, 14w.

[0004] In this electrical architecture 10, two types of currents are distinguished, namely a useful current going from the source 16 to the load 18 and a useless current, called common mode current Imc, which goes from the source 16 to the radiator connected to the chassis and therefore to ground 20 via parasitic capacitors 24.

[0005] In order to reduce the common-mode current Imc, it is known to insert an inductor, called a common-mode inductor 22, as part of an LC filter. This common-mode inductor 22 sees both the useful and waste currents simultaneously, which necessitates sizing this inductor accordingly. Conventional common-mode inductors 22, generally in the form of a toroid, therefore present significant constraints in terms of size and mass. A common mode inductance 22 for an inverter 14 with a power of 50kW generally has a mass greater than 800 grams.

[0006] The common-mode current Imc is essentially due to the parasitic capacitances of the converter transistors 14. Document EP4145505A1 describes how to locally filter the common-mode current by means of a specific local inductance at each transistor. This reduces the stress on the inductance 22 of the input LC filter. However, such a solution implemented by the electrical circuit manufacturer or foundry is expensive and complex to produce.

[0007] The invention aims to effectively remedy the aforementioned drawbacks by proposing an electrical system comprising: - at least one electrical converter comprising a plurality of power transistors, - a casing made of an electrically conductive material, defining an enclosure in which the electrical converter is placed, - said housing comprising a supporting side panel forming a heat sink for the power transistors or behind which is a finned heat sink on which the power transistors are mounted, - said side support panel comprising fixing brackets intended to secure the electrical system to a chassis, - the mounting brackets protrude beyond the thickness of the supporting side wall, so that the supporting side wall is positioned at a distance from the chassis, - each mounting tab having a corresponding local inductance, so that a common-mode current from the power transistors and passing through the heatsink can be channeled to the chassis via the local inductances of the mounting tabs, forming a high-frequency impedance path between the heatsink and the chassis.

[0008] The invention thus makes it possible to reduce the common-mode current and therefore to reduce the mass and size of the common-mode inductance of the power converters while maintaining the rigidity expected during vibration tests. Indeed, the added mass due to the local inductances (a few tens of grams per mounting tab) is negligible compared to the reduction of the common-mode inductance mass by a factor of 2 to 10. The invention also makes it possible to increase the dV / dT switching ratio of the power converter transistors.The invention also has the advantage of being simple to implement and low cost.

[0009] According to one embodiment of the invention, each local inductance comprises at least one ferromagnetic core disposed on or at least partly inside a corresponding mounting tab.

[0010] According to one embodiment of the invention, the ferromagnetic core is disposed at least partly inside a correspondingly shaped groove made in a fixing tab.

[0011] According to one embodiment of the invention, the ferromagnetic core is glued or brazed onto the housing around the fixing tab.

[0012] According to one embodiment of the invention, the ferromagnetic core is arranged around a pad extending between the housing and a corresponding fixing tab.

[0013] According to one embodiment of the invention, the ferromagnetic core is arranged between a face of a fixing tab and a corresponding retaining plate, stiffening pads extending between a face of the fixing tab and a face opposite the retaining plate.

[0014] According to one embodiment of the invention, individual ferromagnetic cores are arranged around each stiffening pad.

[0015] According to one embodiment of the invention, the ferromagnetic core takes the form of a tile provided with holes for the passage of the fixing member and the stiffening pads.

[0016] According to one embodiment of the invention, the ferromagnetic core is mounted between two walls of a spacer connected to each other by a connecting stud around which the ferromagnetic core is arranged.

[0017] According to one embodiment of the invention, the ferromagnetic core is made up of a ring of round, rectangular or ovoid shape, or any other geometric shape suitable for the application.

[0018] According to one embodiment of the invention, the ferromagnetic core is a single piece.

[0019] According to one embodiment of the invention, the ferromagnetic core is made in two parts assembled together.

[0020] According to one embodiment of the invention, the fixing tabs are made at least partly of a ferromagnetic material constituting the local inductances of the fixing tabs.

[0021] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0022] [Fig-1] The [Fig.1], already described, is an electrical architecture with converters static electrical components equipped with a common mode inductance designed to reduce the common mode current due to the parasitic capacitances of the transistors in an inverter;

[0023] [Fig.2a] [Fig.2b] [Fig.2c] Figures 2a, 2b and 2c are perspective views and in cross-section from different viewing angles of an electrical system housing equipped with mounting tabs incorporating local inductances according to the invention;

[0024] [Fig.3] Fig.3 is a schematic side view illustrating the empty space provided between the housing according to the invention and the mounting chassis;

[0025] [Fig. 4a] [Fig. 4b] Figures 4a and 4b are a perspective view of different forms of ferromagnetic nuclei according to the invention;

[0026] [Fig.5] Fig.5 is a perspective view representing a first variant of realization of a local inductance of the fixing tab according to the invention;

[0027] [Fig.6] Fig.6 is a schematic representation of a second variant of realization of a local inductance of the fixing tab according to the invention;

[0028] [Fig.7] Fig.7 is a schematic representation of a third variant of realization of a local inductance of the fixing tab according to the invention;

[0029] [Fig.8] The [Fig.8] is a schematic representation of a fourth embodiment of a local inductance of the fixing leg according to the invention;

[0030] [Fig.9] Fig.9 is a schematic representation of a fifth variant of realization of a local inductance of the fixing tab according to the invention;

[0031] [Fig. 10] The [Fig. 10] is a schematic representation of a sixth embodiment of a local inductance of the fixing lug according to the invention.

[0032] It should be noted that, in the figures, structural and / or functional elements common to the different embodiments may have the same reference numerals. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0033] Figures 2a, 2b and 2c show an electrical system 30 comprising a housing 31 made of an electrically conductive material delimiting an enclosure 32 in which at least one electrical converter 14 is disposed. The housing 31 is an electromagnetic compatibility (EMC) housing 31 allowing to avoid electromagnetic disturbances which are troublesome for any electrical component in the environment of the system.

[0034] The electrical converter 14 comprises a plurality of power transistors. The electrical converter 14 is, for example, an inverter 14. This electrical converter 14 is integrated into an electrical architecture analogous to that of [Fig. 1] arranged within the housing 31.

[0035] More specifically, the parallelepiped-shaped housing 31 comprises a plurality of side walls 33.1-33.6 delimiting the enclosure 32. One of the side walls, in this case wall 33.1, referred to as the "support side wall," carries the electrical converter 14 and has mounting tabs 37 for securing the electrical system 30 on a chassis 36 (see [Fig.3]). The chassis 36 takes, for example, the form of a structural element of an aircraft.

[0036] In order to dissipate heat from the power converter 14, said power converter 14 is mounted on a heat sink 35. The heat sink 35 may be formed by the supporting side wall 33.1. The power converter 14 is then mounted directly against an inner face of the supporting side wall 33.1 facing the interior of the enclosure 32. When the heat sink 35 is formed by the supporting side wall 33.1, the wall 33.1 may be formed by a plate within which channels for circulating a cooling fluid are defined. The housing 31 is then provided with an inlet and an outlet for the cooling fluid, for example, oil or water containing antifreeze.

[0037] Alternatively, the radiator 35 may be a finned radiator mounted on the side support wall 33.1 by which the housing 31 is attached to the chassis 36. A fan 34, visible in [Fig. 2a], may be mounted on the housing 31 to generate an internal airflow to dissipate heat from the converter 14 by convection. The housing 31 may also include connectors 39 for receiving power and / or control signals from the electrical system 30.

[0038] The mounting brackets 37 project from an edge of the supporting side wall 33.1. Each mounting bracket 37 has an opening for the passage of a fastener, such as a screw, stud, rivet, or any other fastener suitable for the application. The mounting brackets 37 may be right-angled.

[0039] The mounting tabs 37 can be made as a single unit with the supporting side wall 33.1. The mounting tabs 37 can be brazed or sintered onto the housing 31. According to one embodiment, the housing 31 has four mounting tabs 37 arranged at the four corners of the supporting side wall 33.1. Alternatively, the housing 31 may have fewer or more than four mounting tabs 37.

[0040] The mounting tabs 37 project beyond the thickness of the support side wall 33.1, such that the support side wall 33.1 is positioned at a distance from the chassis 36 when the housing 31 is fixed to the chassis, as shown in [Fig. 3]. For example, a gap 38 is provided between the support side wall 33.1 and the chassis 36, having, for example, a thickness of approximately 0.5 mm. The thickness of the gap 38 is adjusted according to the order of magnitude of the common-mode current intensity. In other words, the mounting tabs 37 protrude from the plane of the support side wall 33.1. The protrusion is referred to as D in [Fig. 2c]. The protrusion of the fixing tabs 37 can be achieved by means of a chamfer or by an extra thickness of the fixing tabs 37.1.

[0041] Each mounting tab 37 has a corresponding local inductance 40, so that a common-mode current from the power transistors of the converter 14 and passing through the heatsink 35 can be channeled to the chassis 36 via the local inductances 40 of the mounting tabs 37 forming a high-frequency impedance path between the heatsink 35 of the converter 14 and the chassis 36.

[0042] The mounting tabs 37 thus have a dual function, namely a mechanical fixing function and a common mode current channeling function to the chassis 36 to ground.

[0043] It is important that each of the mounting tabs 37 be associated with a local inductance 40 in order to prevent the common mode current from finding a path of lower impedance than that through the local inductances 40 of the mounting tabs 37.

[0044] Each local inductance 40 may include at least one ferromagnetic core 41 disposed on or at least partly inside a corresponding mounting tab 37.

[0045] In the embodiment of figures 2a to 2c, the ferromagnetic core 41 is disposed at least partly inside a correspondingly shaped groove 42 formed in a mounting tab 37.

[0046] The ferromagnetic core 41 can be a ring of round shape (see [Fig. 4a]), rectangular shape (see [Fig. 4b]), square shape, ovoid shape, or any other geometric shape suitable for the application. The term "ring" thus refers to a ferromagnetic core 41 having a closed circumference defining an internal opening and which can take various forms.

[0047] The ferromagnetic core 41 can be a single piece, as shown in [Fig. 4a]. Alternatively, the ferromagnetic core 41 is made of two parts joined together, in particular by bonding or sintering, as shown in [Fig. 4b]. A two-part ferromagnetic core 41 can facilitate core replacement. The ferromagnetic core 41 can be made of a ferromagnetic material selected from: ferrite, or any other iron-, cobalt-, and / or nickel-based material. The dimensions of the ferromagnetic core 41 are adapted according to the order of magnitude of the common-mode current intensity.

[0048] In the embodiment of [Fig.5], the ferromagnetic core 41 is glued or brazed onto the housing 31 around the mounting tab 37. In this case, it may be advantageous to use a two-part ferromagnetic core 41.

[0049] In the embodiment of [Fig. 6], the ferromagnetic core 41 is arranged around a stud 45 extending between the housing 31 and a corresponding mounting tab 37. The ferromagnetic core 41 has a cross-section with a shape corresponding to that of the stud 45, in particular a round, rectangular, square or ovoid shape, or any other shape suitable for the application.

[0050] In the embodiment of [Fig.7], the ferromagnetic core 41 is arranged between a face of a fixing tab 37 and a corresponding retaining plate 46.

[0051] Stiffening pads 50 extend between a face of the fixing tab 37 and a face opposite the retaining plate 46. Individual ferromagnetic cores 51 are arranged around each stiffening pad 50. The individual ferromagnetic cores 51 have a cross-section having a shape corresponding to that of the stiffening pads 50, in particular a round, rectangular, square or ovoid shape, or any other shape suitable for the application.

[0052] A fastener 47, such as a screw, stud or rivet or any other type of fastener suitable for the application, is inserted into a passage opening made in the fixing tab 37, an opening in the ferromagnetic core 41 and a passage opening in the retaining plate 46,

[0053] The embodiment of [Fig.8] is analogous to that of [Fig.7] except that the ferromagnetic core 41 takes the form of a tile 54 provided with holes for the passage of the fixing member 47 and the stiffening studs 50. The tile 54 has the form of a flat plate of low thickness.

[0054] In the embodiment of [Fig.9], the ferromagnetic core 41 is mounted between two walls 55 of a spacer 56 connected to each other by a connecting stud 57 around which is arranged the ferromagnetic core 4L. The connecting stud 57 may be hollow to allow the passage of a fastener 58, such as a screw, a stud or a rivet or any other type of fastener suitable for the application, also inserted inside an opening made in the fixing tab 37.

[0055] In the embodiment of [Fig. 10], the fixing tabs 37 are made at least partly of a ferromagnetic material constituting the local inductances 40 of the fixing tabs 37.

[0056] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0057] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

Demands

1. Electrical system (30) comprising: - at least one electrical converter (14) comprising a plurality of power transistors, - a housing (31) made of an electrically conductive material delimiting an enclosure (32) in which the electrical converter (14) is disposed, - said housing (31) comprising a supporting side wall (33.1) forming a heat sink (35) for the power transistors or behind which is a finned heat sink on which the power transistors are mounted, - said supporting side wall (33.1) comprising mounting tabs (37) for securing the electrical system (30) to a chassis (36), characterized in that the mounting tabs (37) extend in projection relative to a thickness of the supporting side wall (33.1), so that the supporting side wall (33.1) is disposed at a distance from the chassis (36), - each mounting tab (37) having a corresponding local inductance (40), so that a common mode current from the power transistors and passing through the heatsink (35) can be channeled to the chassis (36) via the local inductances (40) of the mounting tabs (37) forming a high-frequency impedance path between the heatsink (35) and the chassis (36).

2. Electrical system according to claim 1, characterized in that each local inductance (40) comprises at least one ferromagnetic core (41) disposed on or at least partly inside a corresponding mounting tab (37).

3. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is disposed at least in part inside a correspondingly shaped groove (42) made in a fixing tab (37).

4. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is glued or brazed onto the housing (31) around the fixing tab (37).

5. An electrical system according to claim 2, characterized in that the ferromagnetic core (41) is arranged around a stud (45) extending between the housing (31) and a corresponding mounting tab (37).

6. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is disposed between a face of a fixing tab (37) and a corresponding retaining plate (46), stiffening pads (50) extending between a face of the fixing tab (37) and an opposite face of the retaining plate (46).

7. Electrical system according to claim 6, characterized in that the ferromagnetic core (41) takes the form of a tile (54) provided with holes for the passage of the fixing member (47) and the stiffening pads (50).

8. Electrical system according to claim 2, characterized in that the ferromagnetic core (41) is mounted between two walls (55) of a spacer (56) connected to each other by a connecting pad (57) around which the ferromagnetic core (41) is arranged.

9. Electrical system according to any one of claims 2 to 8, characterized in that the ferromagnetic core (41) is constituted by a ring of round, rectangular or ovoid shape, or any other geometric shape suitable for the application.

10. Electrical system according to claim 1, characterized in that the fixing tabs (37) are made at least partly of a ferromagnetic material constituting the local inductances (40) of the fixing tabs (37).

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